Satellite fuel tanks are complex devices that use various means to deliver fuel to propulsion systems of the space craft. In a zero or low gravity environment, separating the liquids from pressurizing gases in order to deliver them in sufficient quantities to support mission requirements is difficult. Often, this process is performed with a propellant management device (PMD) that utilizes surface tension and capillary action to transport the liquid fuel. It is imperative that the tank and PMD materials are compatible and wettable with the liquid fuel chemicals such as hydrazine. It is known in the art that materials such as titanium and titanium alloys are used for this purpose because of their high chemical compatibility and wettability with hydrazine and other propellants and oxidizers used to fuel satellites.
One requirement for low earth orbiting (LEO) satellites is the ability to retain enough fuel for a final de-orbit maneuver at end of life. The purpose of this activity is to position the space craft in a controlled re-entry trajectory that allows it to fall into the ocean, thereby reducing the loss of life and property should the debris fall into a populated area. Unfortunately, the amount of fuel needed for this final action could otherwise enable the space craft to remain functional for a period of up to several years if the end of mission re-entry were uncontrolled. Uncontrolled re-entry requirements are that all but a negligible portion of the space craft burn up (demise) during re-entry.
Designs for demise programs have emphasized replacing components fabricated from higher melting point materials such as steels and titanium with lower melting material such as aluminum to increase demisability during re-entry. The fuel tanks for the NASA Global Precipitation Measurement satellite (GPM) have been designed with aluminum fuel tanks and PMDs for this purpose. A special surface treatment to increase the chemical compatibility and wettability of aluminum alloys used for the GPM components has been expensive, labor intensive, and difficult to verify in completed tank structures.